In general, an electrostatic earphone has excellent frequency response and provides a very broad range of playing an audio frequency signal.
However, the operation of the electrostatic earphone is driven by boosting a low voltage (such as several volts) to a high voltage (such as several hundreds of volts). In general, a conventional electrostatic earphone uses utility power as the low-voltage power source. If the power source is changed to a primary battery or a secondary battery, then the efficiency of converting the low voltage to the high voltage will be affected significantly, or the primary or secondary battery may be even damaged during the conversion which will affect the service life of the battery adversely.
In addition, the power source of the conventional electrostatic earphone is maintained at a power supplying state, no matter whether the electrostatic earphone has received an input of the audio frequency signal. Therefore, the power supply method intangibly causes a waste of energy and the using time of the primary or secondary battery. Obviously, the conventional electrostatic earphone requires an improved circuit to overcome the aforementioned problem.